Java ResourceBundle - containsKey() Method

The java.util.ResourceBundle.containsKey() method is used to determine whether the given key is contained in this ResourceBundle or its parent bundles.

Syntax

public boolean containsKey(String key)

Parameters

Return Value

void type.

Exception

Throws NullPointerException, if key is null.

Example:

Lets assume that we have resource file called Greetings_en_US.properties in the CLASSPATH with the following content. This file contains local message for US country.

greet = Hello World!

In the below Java program, the java.util.ResourceBundle.containsKey() method is used to check if a given key is contained in the above mentioned resource bundle Greetings_en_US.properties or its parent bundles.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a resource bundle in specified locale
    ResourceBundle bundle = ResourceBundle.getBundle("Greetings", Locale.US);

    //printing the text assigned to "greet" 
    //key in the bundle
    System.out.println(bundle.getString("greet")); 

    //check if the bundle contains "greet" keyword
    System.out.println(bundle.containsKey("greet")); 

    //check if the bundle contains "welcome" keyword
    System.out.println(bundle.containsKey("welcome")); 
  }
}

The output of the above code will be:

Hello World!
true
false